Cross-linked separation membrane and process for pervaporation

Abstract

A preparation membrane for pervaporation which comprises a crosslinked reaction mixture of a polyvinyl alcohol or polyvinyl alcohol copolymer and a polystyrene sulfonic acid or polystyrene sulfonic acid copolymer. A method for separating a mixture of water and an organic compound by using the membrane is also disclosed.

What is claimed is: 
     
       1. A separation membrane for pervaporation which comprises an intermolecular crosslinked reaction product of a mixture consisting essentially of a polyvinyl alcohol or polyvinyl alcohol copolymer and a polystyrene sulfonic acid or polystyrene sulfonic acid copolymer. 
     
     
       2. A membrane according to claim 1, wherein the sulfonic acid in the crosslinked reaction product is introduced in the form of a sulfonate group. 
     
     
       3. A membrane according to claim 2, wherein the sulfonate is an alkali metal sulfonate. 
     
     
       4. A membrane according to claim 1, wherein the membrane is obtained by applying a mixture of polyvinyl alcohol and polystyrene sulfonic acid on a porous supporting material and then subjecting the mixture to a crosslinking treatment. 
     
     
       5. A membrane according to claim 4, wherein the mixing ratio of polyvinyl alcohol and polystyrene sulfonic acid is in the range of 1.5 to 5.0 parts by weight of polyvinyl alcohol per 1 part by weight of polystyrene sulfonic acid. 
     
     
       6. A membrane according to claim 4, wherein the crosslinking treatment is effected by heating at 100° to 150° C. 
     
     
       7. A membrane according to claim 4, wherein the porous supporting material is an ultrafiltration membrane. 
     
     
       8. A membrane according to claim 4, wherein the porous supporting material is made of polyacrylonitrile copolymer. 
     
     
       9. A method for separating a mixture of water and an organic compound which comprises the steps of (a) contacting one side of a separation membrane for pervaporation comprising an intermolecular crosslinked reaction product of a mixture consisting essentially of a polyvinyl alcohol or polyvinyl alcohol copolymer and a polystyrene sulfonic acid or polystyrene sulfonic acid copolymer with a liquid feed mixture containing water and at least one organic compound; and   (b) withdrawing from the other side of said membrane a permeate in a vapor state, said permeate containing water vapor in a concentration higher than that in the feed mixture.   
     
     
       10. A method according to claim 9, wherein the organic compound is an aliphatic alcohol. 
     
     
       11. A method according to claim 10, wherein the aliphatic alcohol is ethanol. 
     
     
       12. A method according to claim 9, wherein the permeate contains at least 80% by weight of water. 
     
     
       13. A method according to claim 9, wherein the sulfonic acid contained in the crosslinked product is in the form of a sulfonate. 
     
     
       14. A method according to claim 13, wherein the sulfonate is an alkali metal sulfonate. 
     
     
       15. A membrane according to claim 7, wherein the porous supporting material is made of polyacrylonitrile copolymer.